It is not possible to configure port forwarding rules for identical TCP or UDP ports or for the IP protocols ESP and GRE in the FRITZ!Box. When attempting to configure a port forwarding rule, the error message "ERROR: Entry already exists" is displayed.

1 Cannot forward the same port or IP protocol more than once

Only one port forwarding rule can be configured in the FRITZ!Box for each TCP or UDP port, or the IP protocols ESP and GRE. As a rule, it is not possible to configure several port forwarding rules for the same port or the IP protocols ESP and GRE in network routers such as the FRITZ!Box.

Note:The FRITZ!Box checks all incoming and outgoing data packets and automatically rejects unrequested data from the Internet (Stateful Packet Inspection). The FRITZ!Box uses the NAT (Network Address Translation) mechanism to check incoming data and determine which port they are addressed to, which IP protocol they are transporting, and which device they are to be forwarded to. If ports or IP protocols are forwarded more than once, it is no longer clear which device the data is for. Therefore, it is not possible to configure multiple forwarding rules with NAT.

Workaround

If several network devices (for example computers, NAS systems, game consoles) or Internet applications such as chat software or online games require the same TCP or UDP port for incoming connections from the Internet, configure the devices or applications so that they all use different ports:

Important:IP protocols ESP and GRE can only be forwarded for one device. There is no workaround for these IP protocols.

Configure the network device or Internet application so that connections from the Internet are received by ports that are not used by the FRITZ!Box, other network devices, or other Internet applications.

Important:If you use the same application on several computers, assign different ports for incoming connections in the application on each computer.